Since plasmalogens are the predominant phospholipid constituents of sarcolemma and are selectively hydrolyzed during myocardial ischemia, the goal of the proposed studies is the demonstration that accelerated plasmalogen catabolism is a biochemical mediator of the pathophysiologic sequelae of myocardial ischemia.The identification of accelerated plasmalogen catabolism in the sarcolemmal compartment of Intact ischemic hearts will be achieved by electron microscopic autoradiography employing maximum-likelihood analysis. To discriminate between phospholipase C- and D- mediated plasmalogen polar head group turnover, electrospray mass spectrometry(a divisional resource)will be exploited to quantitate 18/O- labeled phosphocholine and 18/O-labeled phosphatidic acid produced by H2 18/O-labeled cardiac myocytes. Electrophysiologic dysfunction mediated by accelerated plasmalogen polar head group turnover will be assessed in voltage-clamped Sf9 cells (containing overexpressed K+ channels) and neonatal cardiac myocytes that overexpress enzymes catalyzing polar head group remodeling. The effects of calcium-independent PLA2 on electrophysiologic function will be assessed utilizing patch-clamped myocytes perfused with purified calcium-Independent PLA2 in the presence and absence of the specific mechanism-based inhibitor of calcium- independent PLA2 (HELSS). The physiologic role of accelerated plasmalogen catabolism also will be assessed by characterizing protein kinases that are activated by plasmalogen catabolites during ischemia. The scientific environment and resources at Washington University provide a unique opportunity to execute the proposed studies. Taken together, a RCDA would provide support for a multidisciplinary, state-of-the-art approach to directly demonstrate the importance of accelerated plasmalogen catabolism in mediating the pathophysiologic sequelae of myocardial ischemia. Furthermore, a RCDA would provide critical support at this Important juncture in my research career which will facilitate my career goals of identifying the importance of alterations in phospholipid structure and function in mediating cardiovascular dysfunction in clinically relevant disease states.